The invention relates to a continuous hot rolling method of metal blocks for butt-joining a preceding metal block and a succeeding metal block and continuously performing a hot finish rolling, as well as a metal blocks joining apparatus, a table roller conveyor, a poor joined portion removing apparatus and a metal blocks cooling apparatus which are directly used to carry out such method.
Conventionally, in hot rolling lines of metal blocks comprised, for example, of steel, aluminum, copper and the like, the metal blocks to be roller are heated, rough rolled and finish rolled one by one, so as to be finished into a plate having a predetermined thickness. Such a rolling system suffers from disadvantages that a poor threading of the rolled material in the finish rolling inevitably causes the line to stop, and a poor shape of fore end portion and rear end portion of the rolled material results in a low yield.
Therefore, it is a recent trend to carry out an endless rolling in which the metal blocks to be rolled are connected at the fore end and rear end portions thereof prior to the finish rolling and continuously conveyed to the hot rolling line. As prior art in this connection, various proposals are disclosed, for example, in Japanese Patent Application Laid-Open Nos. SHO-58-112601, SHO-60-24401, SHO-61-159285, SHO-61-144203, SHO-62-142082, SHO-62-234679, HEI-4-84609, HEI-4-89120, HEI-5-185109, etc.
According to a general practice, the regions of the metal blocks in the vicinity of their respective end portions are clamped and supported by clamps on the inlet side of the rolling equipment and the to-be-joined portion is heated to an elevated temperature and present and joined by heating means as the endless rolling of the metal blocks is performed. However, in joining the metal blocks which are passed through the abovementioned processes, there still remain various disadvantages such as those described below, in connection with which there have been demands for improvements.
(1) In butt-joining the metal blocks, it is necessary to precisely align the opposite end portions of the blocks and press them with each other. As shown in FIG. 1, the respective end portions of the preceding metal blocks 1 and the succeeding metal blocks 2 are applied with an alternating magnetic field in the direction of thickness, for example, by heating means 3 such as an induction heating coil. When such end portions are heated to an elevated temperature in a short time, even if the metal blocks are fixed and held by clamps, the end portions may shift vertically upon heating and pressing of the metal blocks. That is to say, the joined portion of the metal blocks reaches 1,300-1,500xc2x0 C. in temperature and may be partly melted. Such melted portion has a decreased friction coefficient at the joining interface so that even a slight lack of uniformity in the pressing state may result in a vertical shifting of the plates. This may cause either formation of dissatisfactory joining as shown in FIG. 2 or occurrence of buckling. Thus, when the rolling is performed in such a condition, as shown in FIG. 3, the joined portion of the metal blocks may tilt down when it is bit into the rolls, and deformed and threaded into the base plate of the metal blocks, thereby giving rise to formation of excessively thin portions according to an increased number of rolling passage and a resultant breakage of the plate during the rolling.
(2) The joining apparatus for joining the metal blocks is generally constructed such that a carriage movable on a conveying line of the metal blocks is provided with clamps for fixing the metal blocks, heating means (e.g., an induction heating coil) for heating and metal blocks to an elevated temperature, and pressing means for pressing the end portions of the metal blocks with each other. In this instance, it has been a general practice to cause the heating means to approach the metal blocks only in the use condition and maintain it off the line except during the heating, and such a practice proved to be free from problems. However, the clamps and the pressing means remain mounted on the carriage and hence located on the conveying line of the metal blocks, so that they are subjected to a substantial thermal load and their lives become relatively short. Moreover, the carriage mounting the clamps and the pressing means cannot be attached with table rollers for structural reasons, so that scratches are formed due to the sliding motion of the metal blocks in the carriage when scales are deposited thereon. Further, the maintenance of the clamps and the pressing means cannot be performed except when the transfer of the metal block is stopped or when the rolling is stopped.
(3) In the rolling line provided with a movable-type joining apparatus suitable for joining the metal blocks during the running, there is required an ascending and descending timing control with which the table rollers supporting the metal blocks are moved vertically corresponding to the running of the joining apparatus. A conventional table roller disclosed, for example, in Japanese Patent Application Laid-Open No. HEI-4-357303 lacks in accuracy and reliability as described below. Also, in connection with the driving cylinders for causing the vertical motion of the table rollers, it has been recognized disadvantageous that the hydraulic apparatus has to be large in scale due to a requirement for substantial flow rate of operating oil, thereby giving rise to substantial increase in the power loss and the running cost.
FIG. 4 shows a construction of the equipment disclosed in the abovementioned patent, and FIG. 5 shows a control mechanism relating to a vertical motion of the table rollers disposed in such equipment.
In FIG. 4 mentioned above, since the preceding metal block 1 and the succeeding metal block 2 are joined with each other while they are conveyed, the metal blocks joining apparatus 4 first assumes a waiting position on the upstream side (left side in FIG. 4) of the conveying line for the metal blocks. And, when the rear end portion of the preceding metal block 1 and the fore end portion of the succeeding metal block 2 reach to the joining apparatus 4, both metal blocks 1, 2 are clamped by pinch rolls p1, p2 disposed on the joining apparatus 4 while the joining apparatus 4 runs at the same speed as the conveying speed of the metal blocks, and the rear end portion of the preceding metal block 1 and the fore end portion of the succeeding metal block 2 are heated and pressed until the joining apparatus 4 reaches a predetermined position on the downstream side of the line to complete the joining. On this occasion, the control unit 5 shown in FIG. 5 detects the position of the joining apparatus 4 to operate driving cylinders 7a-7g through an electromagnetic valve 6, respectively, to cause vertical motion of the respective movable table rollers 8a-8g for preventing them from colliding against the joining apparatus 4. In the equipment constructed as above, there is required a control by which the table rollers positioned in front of the joining apparatus 4 are descended when the joining apparatus 4 reaches thereto and the table rollers are ascended immediately after the joining apparatus 4 has passed therethrough. However, there is a problem relating the accuracy and reliability of the electromagnetic valve 6 for performing the control and the vertical motions of the table rollers, so that the joining apparatus 4 and the table rollers 8a-8g may collide against each other. Also, in connection with the driving cylinders 7a-7g for causing the vertical motion of the table rollers 8a-8g, it has been recognized disadvantageous that the hydraulic apparatus has to be large in scale due to a requirement for substantial flow rate of operating oil, and such apparatus has to be continuously operated thereby giving rise to substantial increase in the power loss and the running cost.
(4) In the pressing process of the metal blocks, the butted portions are protruded with a protruding height of 10-25% of the base plate thickness, which is variable depending upon the pressing amount. Such protruding portion is referred to as a xe2x80x9cpoor joined portionxe2x80x9d hereinafter, including burrs and the like. This may be influential on the pressing force of the rolling mill and the tension of the plate, such that the plate may be broken during rolling, either the rolling mills tend to be injured or the uniformity of the plate thickness tends to become poor as the poor joined portion is bit into the rolls, and fallen foils are likely to be formed.
In this connection, there has been proposed a pressing method in which the poor joined portion is sandwiched and crushed in the upward and downward directions or a press-cutting method using a cutter (Japanese Patent Application Laid-Open No. SHO-63-160707). Since, however, the poor joined portion is extended in the fallen foil manner by the pressing method, particularly when thin plates are rolled, the plate may be broken from such extended portion during rolling.
On the other hand, in the press-cutting method using a cutter, it is difficult to coincide the position of the cutter to the poor joined portion during running and the life of the cutters is short due to an increased cutting resistance. When, furthermore, the preceding metal block and the succeeding metal block are out of alignment relative to each other as the metal blocks are joined, the cutter may be caught by the non-aligned portion with the result that the plate is broken or the cutter is injured. Therefore, not only type cost or the cutter is injured. Therefore, not only the cost for the cutter increases, but also there has been a limitation in connection with improvement in the manufacturing productivity.
Besides, as means for removing the poor joined portion, there have been known hot scarfing method and hot grinding method. However, both of them have been dissatisfactory to perform removal, within a short time of about 1 second, of a surface of the metal blocks at a temperature in excess of 1,000xc2x0 C. or more, as in the continuous hot rolling aimed at by the invention.
It is an object to provide a novel method for dissolving all of the conventional various problems in connection with implementation of a continuous hot rolling, and various apparatuses which are used directly for carrying out said method.
The various problems described above as the tasks of the invention can be advantageously attained by the constituent features described below.
Specifically, the invention provides a continuous hot rolling method comprising the steps of cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other and thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step of restraining a region of each of the metal blocks extending from a clamping position to the end portion thereof for preventing a level change of the metal blocks upon heating and pressing the metal blocks (the first invention).
The invention further provides a continuous hot rolling method comprising the steps of cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step of restraining a region of each of the metal blocks passed by a magnetic flux and extending from a clamping position to the end portion thereof, by means of a plurality of holding members, for preventing a level change of the metal blocks upon heating and pressing the metal blocks by an induction heating coil, said holding members being arranged spaced apart from each other on surfaces of the metal blocks and having a width which is not greater than five times of a penetration depth of an induced current by the heating coil (the second invention).
The invention further provides a continuous hot rolling methods comprising cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other and thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step of arranging a plurality of holding members on a magnetic flux passing region of each of the metal blocks extending from a clamping position to the end portion thereof, for preventing a level change of the metal blocks upon heating and pressing the metal blocks by an induction heating coil, the holding members being arranged spaced apart from each other on surfaces of the metal blocks and each having a width which is not greater than five times of a penetration depth of an induced current by the heating coil, thereby restraining the metal blocks while maintaining an insulating state between the holding members and the metal blocks (the third invention). In this instance, it is preferable to perform the joining while blowing at least one of non-oxidizing gas and reducing gas onto a to-be-joined face and a joined portion of the metal block.
The invention further provides a continuous hot rolling method comprising cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other and thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step, upon joining the metal blocks by a movable joining apparatus, of escaping downwardly those table rollers for conveying the respective metal blocks, which are situated in a region below the movable joining apparatus, and returning the table rollers to an initial level in a conveying region of the respective metal blocks (the fourth invention).
The invention further provides a continuous hot rolling method comprising cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other and thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step of shaving off a poor joined portion from a surface of a base plate by a predetermined depth, upon removal of the poor joined portion of the metal blocks formed by pressing (the fifth invention). In this instance, it is preferable to control a rotating cutter upon shaving off the poor joined portion, such that a circumferential speed thereof is 50-120 m/s.
The invention further provides a continuous hot rolling method comprising cutting a rear end portion of a preceding metal block and a fore end portion of a succeeding metal block, respectively, heating and pressing the metal blocks to each other and thereby joining them with each other, and subsequently performing a finish rolling, wherein the method further comprises the step of cooling the joined portion after joining the metal blocks and before and/or after removing the poor joined portion (the sixth invention).
The invention further provides a metal block joining apparatus in a continuous hot rolling, which comprises heating means for heating the metal blocks to an elevated temperature, clamps having seizing portions which protrude toward the end portion of the metal block for clamping a preceding metal blocks and a succeeding metal block one above the other, and pressing means for moving and pressing at least one of the preceding metal block and the succeeding metal block toward the other of the metal blocks (the seventh invention).
The invention further provides a metal block joining apparatus in a continuous hot rolling, which comprises induction heating coil for heating the metal blocks to an elevated temperature, clamps for clamping and restraining a preceding metal block and a succeeding metal block one above the other, and pressing means for moving and pressing at least one of the preceding metal block and the succeeding metal block toward the other of the metal blocks, each of the clamps having a notch portion notched in a comb-like manner at regular intervals along a widthwise direction of the metal block in a magnet flux region of a seizing portion which protrudes form a clamping and supporting portion of the metal block toward an end portion thereof (the eighth invention).
The invention further provides a metal block joining apparatus in a continuous hot rolling, which comprises induction heating coils for heating the metal blocks to an elevated temperature, clamps for clamping and restraining a preceding metal block and a succeeding metal block one above the other, and pressing means for moving and pressing at least one of the preceding metal block and the succeeding metal block toward the other of the metal block, at least one of the clamps having a notch portion notched in comb-like manners at regular intervals in a widthwise direction of the metal block, and an insulation material bridged between the metal blocks in a region over both of the metal blocks (the ninth invention). In this instance, it is preferable to provide the clamp with a nozzle for blowing at least one kind of an non-oxidizing gas and a reducing gas onto a to-be-joined face and a joined portion of the metal blocks.
The invention further provides a metal block joining apparatus in a continuous hot rolling, which comprises heating means for metal blocks, clamps for clamping and restraining a preceding metal block and a succeeding metal block one above the other to thereby align levels of the metal blocks, and pressing means for moving and pressing at least one of the preceding metal block and the succeeding metal block toward the other of the metal blocks, moving means for moving each of said means between an on-line position and an off-line position, and vertically movable table rollers for supporting the metal block at a region where each of the means by the moving means have been moved to the -off-line position (the tenth invention).
The invention further provides a metal block conveying table roller conveyor in a continuous hot rolling, which comprises a plurality of table rollers for supporting the metal blocks at a plurality of positions along a longitudinal direction thereof, cylinders arranged below and supporting the respective table rollers, and a hydraulic circuit including a hydraulic pipe which communicates cylinder heads with each other, for maintaining an inner pressure of each of the cylinder heads at a constant pressure (the eleventh invention).
The invention further provides a poor joined portion removing apparatus for metal blocks in a continuous hot rolling, which comprises a pair of upper and lower rotating cutters for cutting and removing a poor joined portions of the metal blocks, a rotating speed control means for controlling the rotating cutters at a circumferential speed of 50-120 m/s, tracking means for tracking a joined portion of the metal blocks, and a control means for controlling cutting by the rotating cutter according to a tracking state of the metal blocks (the twelfth invention).
The invention further provides a metal block cooling apparatus in a continuous hot rolling, which comprises a cooling nozzle for ejecting a cooling medium at one or more positions of a region which extends from an input side to an output side of a poor joined portion removing apparatus for removing a poor joined portion formed upon pressing the metal blocks (the thirteenth invention).
According to the invention, a region of the metal blocks extending from a position fixed by the clamps to the end portion thereof is restrained for preventing the end portion from deformation upon heating of the metal blocks to an elevated temperature, and thereby restricting a vertical movement thereof. It is thus possible to avoid joining of the metal blocks which have been disclosed relative to each other, and prevent occurrence of bucklings (the first to third inventions and the seventh to ninth inventions).
According to the invention, furthermore, the clamps, the heating means and the pressing means constituting the joining apparatus are individually movable so that it is possible to decrease the thermal load applied to such means and extend the life of the apparatus (the tenth invention).
According to the invention, furthermore, the table rollers for conveying the metal blocks are forced to escape to a position below the joining apparatus upon arrival thereof, and to return to the metal blocks conveying region immediately after passage of the joining apparatus. Therefore, a complicated control is not required in connection with the vertical motion of the table rollers for positively preventing collision of the table rollers against the joining apparatus, and it is possible to simplify the apparatus (the fourth and eleventh inventions).
According to the invention, furthermore, the poor joined portion formed by pressing the metal blocks is adapted to be shaved off from the surface of the base plate, thereby making it possible to realize a smooth rolling over the entire length of the metal blocks including the joined portion (the fifth and twelfth inventions).
According to the present invention, furthermore, when the poor joined portion formed by pressing the metal blocks are removed, the region of the metal blocks including the protruding portion and the joined portion is cooled during a period beginning from before initiation of the removal and lasting after completion of the removal. By carrying out the cooling before the removal of the poor joined portion, chips can be advantageously prevented from depositing onto the outer thereby extending the cutter life. Moreover, by carrying out the cooling before and after the removal, it is possible to realize an improved uniformity in temperature of the base plate and the joined portion (the sixth and thirteenth inventions).